AHC: Communism sweeps over Southeast Asia

During the Cold War, the principle of the domino theory held much sway among anti-Communist nations, especially the United States. In 1965, this principle would force said nations into the Vietnam War. Alas, after 10 years and thousands of people dead, the United States would retreat from Vietnam, leaving the Communists to march into Saigon and reunify North and South Vietnam. The US's failure in Vietnam War also resulted in Laos and Cambodia turning to Communism.

However, this would be where the domino effect ended in our timeline. Southeast Asia never underwent a wave that turned the region into a Communist utopia like the US feared.

But, that is my challenge. In some way, alter history so that the domino effect sweeps not only over Indochina, but the rest of Southeast Asia such as the Philippines, Indonesia and maybe even Australia.
 
It would be pretty unprecedented for a liberal-democracy of Australia's degree of socioeconomic development to go Communist in the late 20th Century, without an invasion of some sort(which I really doubt the heirs of Ho Chi Minh would be capable of carrying out).

As for the other places on your list, I'm wondering if the nationalistic nature of SE Asian Communism would limit its ability to spread from country to country, at least in the way envisioned by the domino theory. The Khmer Rouge were originally Vietnamese-aligned, so I guess that might count as a domino, but I think the war against the US originally had a lot to do with their coming to power. It didn't take them too long to become rabidly anti-Vietnamese, and I don't know if they'd have any friendlier relations with Thai Communists.

From a BBC article about the Preah Vihear Temple....

The issue escalated again when Cambodia applied for it be listed as a Unesco World Heritage site in 2008. Thailand wanted it to be a joint Thai-Cambodia listing, but eventually withdrew its objection. The decision enraged Thai nationalists and both sides began a build-up of troops in the area.

In April 2009, soldiers
exchanged fire across the disputed border. More serious trouble flared in February 2011, when at least eight people were killed in several days of fighting. The violence moved westwards to another set of temples in April, before shifting back to Preah Vihear, as widespread clashes forced tens of thousands to flee.

I can't really see the Khmer Rouge being any more conciliatory about this sort of thing than the OTL Cambodian government, even if Thai Communists wanted them to be. Though I guess you could posit a situation where the much-less wackadoodle Hun Sen still comes to power, and for some reason dedicates himself to the spread of revolution in the region, while toning down the hypernationalist rhetoric.

Thailand-Cambodia Temple Dispute
 
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